1. Field of the Invention
The present invention relates to structure for installing a rear cushion in a motorcycle, and to a hydraulic shock absorber with a subsidiary cylinder to be used in a suspension device of the motorcycle.
2. Description of Background Art
In a certain rear suspension mechanism of a motorcycle or the like, a front end of a vehicle body-side rear swing arm is supported in such a manner as to be freely rock-able by a pivot shaft, the rear swing arm is provided with a cushion bracket in the upper portion on the front end side thereof, the lower end of the rear swing arm on the front end side is coupled to the vehicle body side through a link, and the upper and lower portions of the rear cushion are supported between this link and the cushion bracket (See, for example, Japanese Patent Laid-Open No. 2002-68066).
In this conventional structure, a pair of left and right rear swing arms are provided with the above-described cushion brackets so as to make a pair with each other, protruding upward in a substantially mountain shape respectively. Also, each cushion bracket supports the rear cushion at an upper end which becomes a free end, and is supported on the rear swing arm only at the lower end. Therefore, when the cushion bracket is viewed in terms of one side of left and right, each is constructed to, so to speak, cantilever-support the rear cushion. For this reason, in order to secure as great installation rigidity as possible for supporting a heavy load of the rear cushion, the cushion bracket cannot avoid becoming large size, but as a result, the weight has been increased to increase the cost.
In another conventional structure, there is a hydraulic shock absorber with a subsidiary cylinder having a cylinder which is a hydraulic cylinder for generating a damping force, and a subsidiary cylinder to be connected through a crooked oil path from this cylinder, in which there is provided a gas chamber within the subsidiary cylinder (See, for example, Japanese Patent Publication No. 61-7393).
In the situation where an oil path is provided and is connected to a subsidiary cylinder as in the case of the above-described conventional example, when a cylinder contracts at high speed, hydraulic fluid flows through the oil path, and a high reaction force is stored in a gas chamber of the subsidiary cylinder while when the cylinder is changed into expansion, restoration of the gas chamber causes the hydraulic fluid which has flowed into the subsidiary cylinder to return to the cylinder. At this time, since the diameter of the oil path is small, a flow velocity of the hydraulic fluid becomes high, and therefore, there occurs an unexpected damping force. Since, however, such a damping force is not necessary for the intrinsic shock absorber, it is requested to prevent such a damping force from occurring.